The invention described herein may be manufactured and used by or for the Government of the United States of America for government purposes without the payment of any royalties therefor.
The invention relates in general to manual die sets for pressing explosive powder and in particular to manual die sets for pressing explosive powder into hollow cylindrical pellets.
Manual die sets for pressing explosive powder into hollow cylindrical pellets are known. The explosive powder is a highly sensitive explosive molding powder, for example, PBXN-9 or PBXW-11. The manual die set, in combination with a press for supplying the pressing force, presses the explosive powder into hollow cylindrical (donut-shaped) pellets.
FIG. 1 is an elevation view, partially in cross-section, of a known manual die set 10 in a press configuration. FIG. 2 is an elevation view, partially in cross-section, of the die set 10 in a first knockout configuration. FIG. 3 is an elevation view, partially in cross-section, of the die set 10 in a second knockout configuration.
Referring to FIG. 1, manual die set 10 is used to press highly sensitive explosive molding powder into a hollow cylindrical pressed pellet 24 in the following manner. First, the baseplate 22 is fitted into the opening 20 in the bottom of the die 18. A mandrel 16 is inserted in the die opening 20 and into the opening 26 in the baseplate 22. The required amount of molding powder is poured into the die opening 20. Next, the ram 12 with opening 14 is inserted into the top of the die opening 20 and mandrel 16 is inserted into opening 14 in the ram. Pressing force is applied by a press (not shown) to the top of ram 12 until the pellet 24 is formed.
Referring to FIG. 2, the die set 10 is manually turned upside down and placed on a first or mandrel knockout ring 28. An ejector guide 30 having an opening 31 therein is placed on top of baseplate 22 and die 18. A mandrel ejector 32 is inserted in the opening 31 in the ejector guide 30. Pressing force is applied by a press to the top of mandrel ejector 32 so that the mandrel ejector 32 moves downwardly to force the mandrel 16 out of the die set 10. Mandrel ejector 32 and ejector guide 30 are then removed.
Referring to FIG. 3, the manual die set 10 is removed from the mandrel knockout ring 28 of FIG. 2, again turned upside down and then placed on a second or pellet knockout ring 34. Pressing force is applied by a press to the top of ram 14. Ram 14 moves downwardly, ejecting the baseplate 22 (if not already removed manually) and the explosive pellet 24. Ram 14 stops when it contacts the top of die 18.
The process described above requires many time-consuming steps. Die set 10 must be turned upside down twice with the explosive pellet contained therein. The manual die set 10 also includes many pieces of tooling. Only well experienced technicians can handle the die set 10, because of safety concerns associated with turning the die set upside down twice with the explosive pellet therein. Thus, a need exists for a manual die set that overcomes the problems of the manual die set of FIGS. 1-3.
In one embodiment, the present invention provides a manual die set comprising a ram, the ram defining a bore therethrough; a die, the die defining a bore therethrough for reciprocably receiving the ram; a baseplate having an upper portion and a lower portion and defining a bore therethrough, the upper portion of the baseplate being disposed in a bottom of the die bore, the lower portion of the baseplate supporting the die; a knockout ring for supporting the die; a supporting block disposed in an interior of the knockout ring, for supporting the baseplate when the manual die set is in a pressing configuration, the supporting block defining a bore therethrough; and a mandrel, the mandrel being disposed in the ram bore, the baseplate bore and the supporting block bore when the manual die set is in a pressing configuration, the mandrel including an upper large diameter portion, a transition portion and a lower small diameter portion.
Preferably, a diameter of the upper large diameter portion of the mandrel is about 0.050 inches larger than a diameter of the lower small diameter portion of the mandrel. More preferably, the transition portion of the mandrel is disposed in the baseplate bore in the lower portion of the baseplate, when the manual die set is in a pressing configuration.
The manual die set further comprises explosive molding powder disposed in the die bore between the ram and the upper portion of the baseplate, when the manual die set is in a pressing configuration.
The supporting block includes a channel extending from the supporting block bore to an outer surface of the supporting block, the channel having a width at least as large as a diameter of the supporting block bore. The knockout ring includes an opening having a width greater than a diameter of the supporting block such that the supporting block is removable from the interior of the knockout ring via the opening in the knockout ring.
In a preferred embodiment, the ram includes an opening in a top portion thereof, the manual die set further comprising an air cap disposed in the opening in the top portion of the ram, the air cap including a passage therein for air flow from the ram bore, the air cap defining a groove formed therein, the manual die set further comprising an O-ring disposed in the groove in the air cap. The ram includes at least one air passage in a lower portion thereof, the at least one air passage extending from the ram bore to an external surface of the ram.
The supporting block includes a second channel formed in a bottom portion thereof, the second channel extending from a point beyond the supporting block bore, in a direction opposite from a direction of the first channel, to the outer surface of the supporting block.
The lower small diameter portion of the mandrel includes an undercut formed therein, the undercut being located in the second channel of the supporting block, the manual die set further comprising a lock which is removably inserted in the second channel to engage the undercut in the mandrel thereby preventing vertical motion of the mandrel.
Another aspect of the invention is a method of pressing hollow cylindrical pellets comprising pouring explosive molding powder into a die bore; pressing a ram a first time to compress the explosive molding powder between the ram and a baseplate to form a pellet; removing a supporting block from the manual die set via an opening in a knockout ring; pressing the ram again to eject the pellet from the die; lifting the die from the knockout ring until a bottom of a mandrel is above the pellet; and removing the pellet from an interior of the knockout ring.
Further objects, features and advantages of the invention will become apparent from the following detailed description taken in conjunction with the following drawing.